Mercury oxide electrode; the factory‑supplied reference solution is 1 mol potassium hydroxide.

232 straight-type saturated calomel electrode; the factory‑supplied reference electrolyte is a saturated potassium chloride solution.

Double-junction calomel electrode; the factory‑supplied reference electrolyte is a saturated potassium chloride solution.

The silver chloride electrode has an outer glass diameter of approximately 6 mm, and its factory‑filled reference solution is a 3.5 M potassium chloride solution.